Fuel injection system and cylinder head with a central fuel reservoir

ABSTRACT

A fuel injection system for an internal combustion engine and to a cylinder head for such a fuel injection system, in which a central fuel reservoir is provided between a feed pump and a plurality of injectors to be supplied with fuel, which each communicate with the central fuel reservoir via respective high-pressure lines, and the injectors are mounted in a cylinder head of the engine for injecting fuel into a plurality of combustion chambers, and the fuel reservoir and/or the high-pressure lines are at least partly integrated into the cylinder head of the engine.

FIELD OF THE INVENTION

For supplying fuel to combustion chambers, for instance indirect-injection internal combustion engines, injection systems are usedthat have a central pressure reservoir (common rail), by way of whichhighly compressed fuel is delivered to the various injectors of theengine. In such engines, the highest possible injection pressure isgenerally advantageous, since that makes higher engine power levels andreduced emissions possible.

BACKGROUND OF THE INVENTION

In currently known injection systems for supplying fuel to internalcombustion engines, it is known to embody a central pressure reservoirin the form of a tube which communicates with the various injectors ofthe engine via high-pressure lines and is supplied with fuel form thefuel tank via a feed pump. A tube serving for instance as ahigh-pressure reservoir is known to be disposed parallel to and along acylinder head of a self-igniting internal combustion engine. The tubewalls enclose the storage volume of the high-pressure fuel reservoir, byway of which a common high pressure is generated centrally for thevarious injectors, which inject the fuel into the various combustionchambers of the engine. The injection pressure advantageously varies,depending on the load and rpm of the self-igniting internal combustionengine.

A known fuel injection system is disposed in German published,unexamined patent application DE 199 10 970 A1. Here the fuel is pumpedby a feed pump out of a tank into a central pressure reservoir chamberand from there is carried via a plurality of high-pressure lines torespective injectors for injection into the combustion chambers of theengine. The pressure reservoir chamber of the fuel reservoir is definedby the walls of the tube. To further increase the injection pressure, afurther pressure booster unit may be provided between the fuel reservoirand the injectors. A disadvantage of this fuel injection system is thatthe fuel reservoir, which is disposed on the outside of and in thevicinity of the respective cylinder of the cylinder head, requiresadditional space in the engine compartment. Moreover, in such fuelreservoirs, the maximum height of the pressure level is limited by thewall thicknesses of the tube forming the reservoir chamber and by thevarious connecting lines.

Given the ever-increasing demands made in terms of internal combustionengine emissions and noise, there is a need for further provisions inthe injection system so that the even more-stringent limit valuesexpected in future can still be met.

SUMMARY OF THE INVENTION

Embodying a fuel injection system in accordance with the invention asdefined by the characteristics of claim 1 advantageously reduces thespace required for the injection system. The fuel injection system asproposed herein can be designed for both self-igniting internalcombustion engines and direct-injection gasoline engines. If the fuelinjection system proposed according to the invention is used inself-igniting internal combustion engines, the fuel reservoir isdesigned as a high-pressure fuel reservoir, so as to withstand thepressures required. If the fuel injection system proposed according tothe invention is used in direct-injection gasoline engines, the fuelreservoir can be designed with a wall thickness that takes the lowerfuel pressure level that is required in that case into account.

Because the fuel reservoir is at least partly integrated with thecylinder head of the engine, the pressure reservoir located on theoutside, in the form of a tube, in previously known systems used inself-igniting internal combustion engines can be eliminated. Moreover, acomplicated fastening of the reservoir and connecting tubes is notneeded, because of the integrated embodiment of the reservoir chamber ofthe fuel reservoir in the interior of the cylinder head. Anotheradvantage is that the fuel reservoir can be disposed directly in thevicinity of the various injectors, and as a result the connectingdistances on the high-pressure side form the fuel reservoir into therespective combustion chamber via the injectors are reduced. The spaceavailable in the cylinder head of internal combustion engines thusoptimally utilized in terms of realizing a fuel injection system. Thelines leading to and from the fuel reservoir are likewise advantageouslyembodied in the cylinder head of the engine. Alternatively, thereservoir chamber of the fuel reservoir can be disposed directly on thevarious injectors, so that the connecting lines on the high-pressureside are then omitted entirely.

Another advantage of the invention is that the high pressures prevailingin the fuel reservoir are absorbed by all the material comprising thecylinder head, which material surrounds the reservoir chamber integratedinto it. Thus the stresses that arise in the reservoir chamber need notbe absorbed by the direct wall of a tubular fuel reservoir.

In an advantageous feature of the invention, the fuel reservoir isembodied by a recess in the cylinder head. The shape and size of therecess can vary, depending on the particular storage volume required.Thus by simply providing a recess in the material comprising thecylinder head, the fuel reservoir can be disposed directly and in thevicinity of the injectors of the injection system. Additional fasteningsfor the fuel reservoir are dispensed with entirely. Advantageously, therecess of the fuel reservoir is a cylindrical, elongated recess in thevicinity of and along the injectors, which as a rule are arranged in arow. The connecting distances of the high-pressure lines to therespective injectors are thus as short as possible, and are all equal inlength. In an embodiment of the invention that is advantageous in thisrespect, the high-pressure lines that connect the fuel reservoir to thevarious injectors are embodied as connecting conduits that are integralwith the material comprising the cylinder head.

In a further advantageous feature of the invention, the fuel reservoiris embodied as a cylindrical, elongated bore in the cylinder head. Bydrilling, the shape and position of the fuel reservoir can be producedwith precision, and it can be disposed as close as possible to therespective receiving bores for the injectors by way of which the fuel isinjected into the combustion chambers. As an alternative to this, thefuel reservoir is formed by an insert part in the operation of castingthe cylinder head. This makes production extremely simple and requiresno additional machining steps.

In a further advantageous feature of the invention, the fuel reservoir,for instance in common rail injection systems for self-igniting internalcombustion engines, is embodied by a cylindrical tube which isintegrated into the cylinder head of the engine in a suitable bore orrecess. The stresses and loads from the highly compressed fuel are thusadvantageously absorbed by all the material, comprising the cylinderhead, that surrounds the reservoir tube. The cylindrical tube may beprovided on its ends with suitable attachment devices and connectionpoints, making production and installation simple.

The cylinder head having the characteristics of claim 11, which isintended for operating an internal combustion engine in conjunction witha fuel injection system, has a fuel reservoir and respectivehigh-pressure lines that are at least partly integrated into thecylinder head. “Integrated embodiment” is understood here to mean thatthe reservoir chamber of the fuel reservoir and/or the high-pressurelines are provided by means of recesses or bores in the materialcomprising the cylinder head of the engine itself. As a result, therequired installation volume for the injection system in the enginecompartment is reduced, and additional fasteners for a separatehigh-pressure reservoir located on the outside are dispensed with. Therecesses and conduits of high-pressure connecting lines and of thestorage volume of the high-pressure fuel reservoir in self-ignitinginternal combustion engines, for instance, can advantageously berealized by means of insert cores in the operation of casting thecylinder head, or alternatively by means of cylindrical bores, or by acombination of the two.

DRAWING

The invention will be describe in further detail below in conjunctionwith the drawing.

Shown are:

FIG. 1, a schematic illustration of a first embodiment of a fuelinjection system according to the invention, with a fuel reservoir inthe form of a recess in the cylinder head;

FIG. 2, a sectional view of a second embodiment of a fuel injectionsystem according to the invention, with a fuel reservoir integrated intothe cylinder head directly beside various injectors.

EMBODIMENTS

In FIG. 1, a first embodiment of a fuel injection system according tothe invention is shown schematically, having a fuel reservoirintegrated, in the form of a recess, into a cylinder head. Inself-igniting internal combustion engines, the fuel reservoir isembodied as a high-pressure reservoir (common rail); in direct-injectiongasoline engines, the fuel reservoir is designed for a lower pressurelevel. The fuel injection system proposed according to the invention canbe used both in self-igniting internal combustion engines and indirect-injection gasoline engines.

Fuel is pumped from a fuel tank 11 by a feed pump 2 and is furnished incompressed form in a central fuel reservoir 1, which in self-ignitinginternal combustion engines is designed as a high-pressure reservoir,and from there is delivered to the combustion chambers 38 of the engine.The feed pumped by the feed pump 2 passes via a sealing body 9 to reachthe high-pressure fuel reservoir 1, which according to the invention isembodied as a recess 6 in the interior of, and integrated with, acylinder head 5 of an internal combustion engine. The recess 6, which—inthe case of self-igniting internal combustion engines forms thehigh-pressure fuel reservoir 1 and in the case of direct-injectiongasoline engines forms the fuel reservoir—is an elongated cylindricalrecess 6 in the embodiment shown in FIG. 1 and is disposed in thevicinity of and parallel to fuel injectors 3 that are in line with oneanother. The fuel reservoir 1 communicates via high-pressure lines 4with the various fuel injectors 3 for carrying the compressed fuelonward. In the embodiment shown in FIG. 1, the high-pressure lines 4 arelikewise embodied as connecting conduits 7 integrated into the cylinderhead 5. The recess 6 and the connecting conduits 7, which form thehigh-pressure lines 4, can, in the embodiment shown, be produced in theform of insert cores during the operation of casting the cylinder head 5of the engine. Alternatively, they can equally well be formed bysubsequent drilling of the cylinder head 5. Alternatively, they canequally well be formed by subsequent drilling of the cylinder head 5.

The fuel volume pumped from the fuel tank 11 by the feed pump 2 reachesa high-pressure line segment 12, in which fuel that is at high pressureis pumped in the fuel feeding direction 13. At the entrance to thehigh-pressure fuel line segment 12 into the cylinder head 5, the sealingbody 9 is provided on the cylinder head, and through it the fuel volume,at high pressure, flows into the cylindrical recess 6 inside thecylinder head 5 of the self-igniting internal combustion engine. Whenthe cylinder head 5 of the engine is produced by casting, thecylindrical recess 6 can for instance by produced by means of an insertcore, whose pulling direction is represented in FIG. 1 by referencenumeral 39. Surface machining of the inner wall 14 of the cylindricalrecess 6 can be omitted, if the insert core, which can be removed fromthe cylinder head 5 in the pulling direction 39, is pretreated with aparting agent.

A first branch 17 leading to the fuel injector 3 is located at a spacingmarked by reference numeral 19 from the inlet end of the cylindricalrecess 6. The spacing 19 between the first branch 17 and the inlet endof the cylindrical recess 6 is dependent on the pressure level to whichthe cylindrical recess 6, serving as the high-pressure fuel reservoir 1(in the case of self-igniting internal combustion engines) or as thefuel reservoir 1 (in the case of direct-injection gasoline engines), issubjected via the feed pump 2. The first branch 17 to the fuel injector3 is followed by a further, second branch 18 to a second fuel injector3. The axes of symmetry of the fuel injectors 3, which are provided in anumber corresponding to the number of cylinders of the combustionchambers of an engine that are to be supplied with fuel, are identifiedby reference numeral 16. The fuel injectors 3 are each let intofastening openings 10 that are made in the cylinder head 5.

Insert pieces 15 can advantageously be inserted into the material of thecylinder head 5, forming the high-pressure lines 4 between the interiorof the high-pressure fuel reservoir 1 or fuel reservoir and the fuelinjectors 3 by way of which lines the fuel injectors are subjected tofuel at high pressure. In comparison to previously known high-pressurefuel reservoirs located on the outside, the length of the high-pressurelines 4 is extremely short, so that the high pressure level prevailingin the high-pressure fuel reservoir 1 or fuel reservoir (that is, thecylindrical recess 6) is present directly at the fuel injector 3. Theinsert pieces 15 can likewise be made by means of insert cores, whichcan be disposed at the appropriate points in the mold in the operationof casting the cylinder heads 5. The essentially cylindricallyconfigured insert pieces 15 that form the high-pressure lines 4 eachsurround respective connecting conduits 7, which are embodied with adiameter large enough for an adequate fuel supply.

Advantageously, by means of the provisions of the invention it isattained that the material defining the cylindrical recess 6 inside thecylinder head 5 can be utilized to absorb the pressure forces thatprevail in the high-pressure fuel reservoir 1 or the fuel reservoir 1.The same is true for the material of the cylinder head 5 in theself-igniting internal combustion engine that surrounds both the insertpieces 15 and the fuel injectors 3. The stresses arising from the highpressure prevailing in the interior of the cylindrical recess 6 areabsorbed not only via the direct walls of the high-pressure reservoir,as is usual in reservoirs located outside the cylinder head 5 in theprior art, but is also intercepted by all the surrounding materialcomprising the cylinder head 5. Because of the loss of the materialcomprising the cylinder head 5 in the casting operation, intrinsicstresses are induced, which contribute to reducing stress.

In FIG. 2, a second embodiment of the invention is shown in a sectionalview, with a fuel reservoir which extends along the injectors disposedin the cylinder head and is integrated into the cylinder head.

The high-pressure delivery of fuel to the fuel injectors in this variantembodiment of the invention includes a fuel reservoir 1, which is formedby a cylindrical tube 8 that, in the vicinity of the fuel injectors 3,is let into a recess 6 or 40, of suitable size, in the cylinder head 5of the self-igniting internal combustion engine. The fuel reservoir 1formed by the cylindrical tube 8 communicates directly, via sealingbodies 9, with the various fuel injectors 3, so that separate connectingconduits or lines are not needed.

The injector 3 shown as an example in FIG. 2 is inserted into thecylinder head 5 in a fastening opening 10.

As can be seen from the further exemplary embodiment of the invention,shown in section in FIG. 2, the fuel injector 3 is introduced into thefastening opening 10 in the cylinder head 5. The wall 21 of the injectorbody 20 of the fuel injector 3 rests then on the material, comprisingthe cylinder head 5, that defines the fastening opening 10. To make iteasier to introduce the injector body 20, which includes a lateralattachment flange, into the fastening opening 10, the fastening opening10 is embodied in its upper region with an enlarged cross section, incomparison to the cross section of the injector body 20 below the fuelreservoir 1 that is integrated into the cylinder head 5; inself-igniting internal combustion engines, this fuel reservoir isembodied as a high-pressure reservoir chamber, while in direct-injectiongasoline engines it is embodied as a reservoir chamber that is subjectedto a lower fuel pressure level. In an attachment region embodiedlaterally on the injector body 20, a high-pressure bore 22 extends at anangle 23 to the axis of symmetry 16 of the injector body 20. Thehigh-pressure bore 22 comes to an end in the injector body 20 at aprotuberance 24 formed into the injector body on the side toward theinjector. The protuberance 24 toward the injector surrounds the top sideof the sealing body 9, which in turn is penetrated by a through bore 26that is aligned with the high-pressure bore 22. Below the sealing body9, the fuel reservoir 1 extends—perpendicular to the plane of thedrawing in FIG. 2—in the form of a cylindrical tube 8 that is integratedinto the cylinder head 5. The cylindrical tube 8 acting as the fuelreservoir 1 has a plurality of recesses 26 toward the reservoir, whichare distributed over its circumferential surface. The recesses 26 towardthe reservoir are embodied on the circumferential surface of thecylindrical tube 8 in a number corresponding to the number of fuelinjectors 3 to be supplied with fuel. The sealing bodies 9 represent theconnecting elements between the high-pressure fuel reservoir 1 and theinjector body 20 of the fuel injector 3.

In the variant embodiment shown in FIG. 2, The cylindrical tube 8functioning as a fuel reservoir 1, whose wall is identified by referencenumeral 41, is let into an opening 40 extending perpendicular to theplane of FIG. 2. The opening 40 may be a cylindrical recess 6 as shownin FIG. 1, or a longitudinal bore made in the cylinder head 1, forinstance of a self-igniting internal combustion engine. Analogously, thecylindrical recess 6 may be let into the cylinder head 5 of adirect-injection gasoline engine. The wall 41 of the cylindrical tube 8is surrounded virtually completely by the material 42 comprising thecylinder head 5 of the engine, which material absorbs the incidentmaterial stresses when the cylindrical tube 8 is acted upon by fuel athigh pressure. The cylindrical tube 8 surrounds a hollow chamber 27,which is acted upon by fuel at high pressure via the fuel feed pump 2shown in FIG. 1. With the provisions according to the invention, it isadvantageously possible to have higher pressures in the fuel reservoir1, since the material, surrounding it, of the cylinder head 5 can beused in its entirety for absorbing stresses. With the fuel reservoir 1integrated into the cylinder head 5 in accordance with the invention,less installation space outside the cylinder head is needed, since atubular high-pressure reservoir chamber, located on the outside, inself-igniting internal combustion engines and corresponding supply andhigh-pressure lines are omitted.

The injector body 20 of the fuel injector 3 is fastened in the cylinderhead 5 via a clamping body 29. The clamping body 29 includes areceptacle portion 36, which fits over the head region of the injectorbody 20 of the fuel injector 3. Below that head region, an annularlyconfigured contact face 28 is embodied on the injector body 20, and theclamping body 29 rests on this contact face and presses the injectorbody 20 into a contact face 36 provided on the nozzle end of theinjector body. The injector body 20 of the fuel injector 3 is likewisesurrounded virtually entirely by the material comprising the cylinderhead 5, either of a self-igniting internal combustion engine or of adirect-injection gasoline engine. The clamping body 29 includes a bore30 for a clamping screw 31. By means of the clamping screw 31, theclamping body 29 is secured to the cylinder head 5. The clamping body 29furthermore includes a support 33, which has a rounded feature 34. Therounded feature 34 of the support 33 on the clamping body 29 is bracedon a plane face 32 of the cylinder head 5. By means of the proposedfastening capability, the injector body 20 of the fuel injector 3 can beremoved very easily from the cylinder head 5 of the engine, once theclamping screw 31 is loosened and the clamping body 29 is removed bymeans of a tool that engages the annularly extending contact face 38 ofthe injector body 20 from underneath.

One or more injection openings 37 are located on the nozzle end of theinjector body 20 and are opened and closed by an injection valve, notshown in the sectional view of FIG. 2, of the fuel injector 3. Theinjection openings 37 on the nozzle end of the injector body 20 of thefuel injector 3 subject a combustion chamber 38, shown in sketched formin FIG. 2, of a self-igniting internal combustion engine to fuel that isat high pressure.

Both in the variant embodiment shown in FIG. 1 and in the variantembodiment shown in FIG. 2 of the fuel reservoir 1 proposed according tothe invention, the installation space available in the cylinder head 5of an internal combustion engine is advantageously utilized. In theembodiments proposed by the invention, the stresses caused by the highpressures prevailing in a fuel reservoir 1 in the case where it is usedin a self-igniting internal combustion engine are no longer absorbedsolely by the wall of the fuel reservoir, designed in this case as ahigh-pressure fuel reservoir 1. In the first variant embodiment of theinvention shown in FIG. 1, a high-pressure fuel reservoir 1 can beembodied as a recess 6. In the second variant embodiment, the wall 41 ofthe cylindrical tube 8 is surrounded virtually entirely by material 41comprising the cylinder head 5, so that the material 42, which surroundsthe wall 41 of the cylindrical tube, can be utilized for absorbingstresses. Moreover, by means of the provisions of the invention in bothvariant embodiments, not only fasteners for a fuel reservoir located onthe outside of the cylinder head of the engine but also the installationspace required for them on the outside of the cylinder head 5 can bedispensed with. In addition, the provisions of the invention make forespecially easy installation and removal of the fuel injectors 3 orinjector bodies 20 of the fuel injectors 3. Because of the materialcomprising the cylinder head 5 and surrounding the injector bodies 20 ofthe fuel injectors 3, uniform heat dissipation can be effected into thematerial comprising the cylinder head 5 of a self-igniting internalcombustion engine.

In both types of engines, with only slight changes in view of theprevailing operating pressure level, that is, the fuel pressure, theintegration proposed according to the invention of a fuel reservoir intoa cylinder head 5 of an internal combustion engine, whether it is aself-igniting internal combustion engine or a direct-injection gasolineengine, makes use of the unused installation space at the cylinder head5.

LIST OF REFERENCE NUMERALS

-   1 Fuel reservoir-   2 Fuel feed pump-   3 Fuel injector-   4 High-pressure line-   5 Cylinder head-   6 Cylindrical recess-   7 Connecting conduits-   8 Cylindrical tube-   9 Sealing body-   10 Fastening openings-   11 Fuel tank-   12 High-pressure line segment-   13 Fuel feeding direction-   14 Inner wall of cylindrical recess-   15 Insert piece-   16 Axis of symmetry of fuel injector 3-   17 First branch-   18 Second branch-   19 Spacing from face end of cylindrical recess 6-   20 Injector body-   21 Wall of injector body-   22 High-pressure bore-   23 Angle-   24 Protuberance on side toward injector-   25 Through bore of sealing body 9-   26 Recess toward reservoir for sealing body 9-   27 Hollow chamber-   28 Contact face of injector body-   29 Clamping body-   30 Bore of clamping body-   31 Clamping screw-   32 Plane face of cylinder head-   33 Support for the clamping body-   34 Rounded feature-   35 Receptacle for injector head-   36 Contact face of end of injector body toward nozzle-   37 Injection opening-   38 Combustion chamber-   39 Target direction of insert core-   40 Opening for cylindrical tube on side toward cylinder head-   41 Tube wall-   42 Surrounding cylinder head material

1-11. (canceled)
 12. In a fuel injection system for supplying fuel todirect-injection internal combustion engines, having a central fuelreservoir (1) between a feed pump (2) and a plurality of injectors (3)to be supplied with fuel, which communicate with the central fuelreservoir (1), and the injectors (3) are mounted in a cylinder head (5)of the engine for direct injection of fuel into a plurality ofcombustion chamber, the improvement wherein the fuel reservoir (1) is atleast partly integrated into the cylinder head (5).
 13. The fuelinjection system of claim 12, wherein the fuel reservoir (1) is formedpartly or entirely by a recess (6) in the cylinder head (5).
 14. Thefuel injection system of claim 12, wherein the fuel reservoir (1)comprises a storage volume which is formed by a cylindrical, elongatedrecess (6) in the vicinity of and along the injectors (3) in thecylinder head (5).
 15. The fuel injection system of claim 13, whereinthe fuel reservoir (1) comprises a storage volume which is formed by acylindrical, elongated recess (6) in the vicinity of and along theinjectors (3) in the cylinder head (5).
 16. The fuel injection system ofclaim 12, further comprising high-pressure lines (4) which areintegrated, in the form of connecting conduits (7), into the cylinderhead (5).
 17. The fuel injection system of claim 13, further comprisinghigh-pressure lines (4) which are integrated, in the form of connectingconduits (7), into the cylinder head (5).
 18. The fuel injection systemof claim 14, further comprising high-pressure lines (4) which areintegrated, in the form of connecting conduits (7), into the cylinderhead (5).
 19. The fuel injection system of claim 12, wherein the fuelreservoir (1) is embodied as a cylindrical bore (6) in the cylinderhead.
 20. The fuel injection system of claim 13, wherein the fuelreservoir (1) is embodied as a cylindrical bore (6) in the cylinderhead.
 21. The fuel injection system of claim 14, wherein the fuelreservoir (1) is embodied as a cylindrical bore (6) in the cylinderhead.
 22. The fuel injection system of claim 16, wherein the fuelreservoir (1) is embodied as a cylindrical bore (6) in the cylinderhead.
 23. The fuel injection system of claim 12, wherein the cylinderhead (1) is formed by an insert part in the operation of casting thecylinder head (5).
 24. The fuel injection system of claim 13, whereinthe cylinder head (1) is formed by an insert part in the operation ofcasting the cylinder head (5).
 25. The fuel injection system of claim14, wherein the cylinder head (1) is formed by an insert part in theoperation of casting the cylinder head (5).
 26. The fuel injectionsystem of claim 16, wherein the cylinder head (1) is formed by an insertpart in the operation of casting the cylinder head (5).
 27. The fuelinjection system of claim 12, wherein the fuel reservoir (1) is formedby a cylindrical tube (8), which is integrated into the cylinder head(5) in a bore (40) or recess (6).
 28. The fuel injection system of claim12, wherein the walls of the fuel reservoir (1) are formed by thematerial of the cylinder head (5) itself.
 29. The fuel injection systemof claim 12, wherein one sealing body (9) each is inserted between thefuel reservoir (1) and each of the injectors (3).
 30. The fuel injectionsystem of claim 12, wherein the fuel reservoir (1) for supplying fuel todirect-injection internal combustion engines is designed as ahigh-pressure reservoir.
 31. In a cylinder head (5) for direct-injectioninternal combustion engines, for operating the engine in conjunctionwith a fuel injection system which has a central fuel reservoir (1) thatcommunicates, via respective high-pressure connections (4), with aplurality of injectors (3), and the injectors (3) are mounted infastening openings (10) in the cylinder head (5), the improvementwherein the high-pressure connections (4) and the fuel reservoir (1) areembodied as at least partly integrated into the cylinder head (5).